Fox T-Bird/Cougar Forums

Technical => Engine Tech => Topic started by: Gary3072 on January 23, 2014, 03:50:02 PM

Title: Engine idle goes up when braking...
Post by: Gary3072 on January 23, 2014, 03:50:02 PM
I've noticed lately that my idle goes up a bit when I brake at stoplights, or wherever. As if it "revs" on it's own.  Is this anything serious ?

I also notice sometimes when I start the engine it goes from turning to just running, like it "skips" the actual startup .....

Thanks for any help :)
Title: Engine idle goes up when braking...
Post by: thunderjet302 on January 23, 2014, 06:11:59 PM
Codes?
Title: Engine idle goes up when braking...
Post by: BornInAFord on January 23, 2014, 06:58:03 PM
vacuum leak at one of the t's or hose to the booster?
Title: Engine idle goes up when braking...
Post by: TurboCoupe50 on January 24, 2014, 04:17:13 PM
Quote from: BornInAFord;427819
vacuum leak at one of the t's or hose to the booster?

More likely the booster it's self, any leak in the vac to it would cause a continual high idle...
Title: Engine idle goes up when braking...
Post by: Gary3072 on January 25, 2014, 12:09:33 AM
Is this anything serious ? I am running stock manifolds to a y pipe with no cat, to a pair of flowmasters that are dumped at the axle. I was planning to replace the manifolds with headers and an h pipe, then possible a pair of Stinger tailpipes.
Title: Engine idle goes up when braking...
Post by: jcassity on January 25, 2014, 12:22:27 AM
Before you go on tell us if you have something called Emergency brake off

You ever remember hearing a rather annoying hissing noise kind of like underneath your steering wheel?
Title: Engine idle goes up when braking...
Post by: Gary3072 on January 25, 2014, 12:32:54 AM
No I never heard anything like that....I just sounds like the engine idle going up a bit. Could this be a transmission issue ?
Title: Engine idle goes up when braking...
Post by: Haystack on January 25, 2014, 01:53:00 AM
your brake booster is probably leaking. causing low vacuum pressure, so the car idles up to try to compensate for it.
Title: Engine idle goes up when braking...
Post by: jcassity on January 25, 2014, 08:45:28 AM
Quote from: Gary3072;427865
Is this anything serious ? I am running stock manifolds to a y pipe with no cat, to a pair of flowmasters that are dumped at the axle. I was planning to replace the manifolds with headers and an h pipe, then possible a pair of Stinger tailpipes.

double check again,,,
look at the brake pedal metal bar,, and follow it up to around its pivit point.
you will see the little switch the metal hits to make the tail lights illuminate.

if you see a vacuum line going to a plastic pluger device,, note it.
start the car, push on the brake with your hand,,, listen for a leak around those vac lines.

its either your "automatic emergency brake off" feature or the brake booster,,, or the booster itself,, or that 90deg fitting going into the booster which i believe is a spring loaded one way check valve.